A Patent to Thompson and Johs, U.S. Pat. No. 5,706,212 describes an ellipsometer or polarimeter for use at infrared wavelengths. Described is a system comprising a source of a beam of electromagnetic wavelengths, a polarizer means, a stage for supporting a sample system, an analyzer means and a detector system. Further included is at least one compensator positioned between the source and said stage for supporting a sample or between said stage for supporting a sample and the detector. The preferred embodiment involves use of a dual rhomb shaped compensator which causes essentially no deviation of a beam passing therethrough, even when the compensator is caused to rotate about the beam locus. A Patent to Fukue, U.S. Pat. No. 7,557,919 is identified as it uses concave mirrors to direct beams in an ellipsometer. A Patent to Ames et al., U.S. Pat. No. 6,902,326 describes a reflective off-axis optical apparatus such as a collimator. A Patent to Zawaideh et al. describes an optical metrology system involving two off-axis paraboloid mirrors. A Patent to Wang et al., U.S. Pat. No. 6,879,449 is disclosed as it turned up in a search using key words “off axis reflective” and “ellipsometer”, but is not believed to be particularly relevant. Additional searching was performed using keywords “ellipsometer” and “collimation and provided U.S. Pat. Nos. 7,075,650 and 7,492,455 to Johs et al. and 7,184,145 to Amary et al.
It is interesting to note that searching with keywords “reflective collimation” and KLA, (ie. KLA-Tencor), turned up no Patents. KLA Tencor is acknowledged as having Patents to ellipsometers that use reflective focusing. Some examples of KLA Patents are: U.S. Pat. Nos. 6,734,967 and 5,910,842 to Piwonka-Corle et al.; 6,323,946 and 5,917,594 to Norton, (which do disclose a single mirror reflection beams collimation); and 7,075,630 to Meeks et al.
Even in view of the prior art, need remains for a reflectometer, spectrophotometer, ellipsometer, polarimeter or scatterometer system for use in the infrared range of wavelengths.